[alsa-devel] [PATCH] ALSA: hda - using POS_FIX_LPIB on Broadwell HDMI Audio

Pierre-Louis Bossart pierre-louis.bossart at linux.intel.com
Fri May 9 16:58:18 CEST 2014

On 5/9/14, 5:08 AM, Lin, Mengdong wrote:
> Hi,
> We found the Broadwell HDMI audio regression is introduced by this patch:
> commit dcb32ecd9a533f47ab652c5c5680bc50a7a822cd
> Author: Anssi Hannula <anssi.hannula at iki.fi>
> Date: Tue Apr 8 12:36:42 2014 +0300
> ALSA: hda - Do not assign streams in reverse order
> We'll further check the root cause.
> Since this patch seems only affect the stream ID. Actually Intel GPU tool only find the stream ID is changed by this patch.
> In addition, Haswell HDMI audio is not affected and works well. It seems there is HW behavior difference between HSW and BDW.

It's unlikely that the wallclock is the issue here. LPIB and wallclock 
only make sense for the short link to the GPU, where the data is 
reshuffled. It'd look into how the audio data is inserted in the HDMI 
frame, the fact that the behavior is linked to a channel order or stream 
ID points to GPU-level configuration, not a counter issue at the HDAudio 
controller level.

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